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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Trigger, an active release experiment that stimulated auroral particle precipitation and wave emissions

The experimental design by which a cesium vapor cloud was suddenly released in order to stimulate auroral particle precipitation is described along with the general results obtained. A drastic increase of the field-aligned charged-particle flux was observed with subsequent particle bursts. It is suggested that low-energy acceleration was due to parallel electric fields created by an instability which was driven by field-aligned currents resulting from the plasma injection. Pitch angle scattering in the deep magnetosphere may account for particle precipitation continuing for 130 sec after release.

Holmgren, G.↗
NASA NTRS1980

Observations of waves artificially stimulated by an electron beam inside a region with auroral precipitation

Observations of waves stimulated by artificial injection inside an auroral arc by an electron accelerator mounted on the POLAR 5 sounding rocket are presented. The accelerator produced a pulsed electron beam with currents up to 130 mA and energies up to 10 keV; emissions after the end of beam injection were generated by perturbations in the ambient plasma near the accelerator during beam injection. These emissions were independent of the electron beam direction along the geomagnetic field. The high frequency emission observed after beam injection correlated with the passage through an auroral arc; the low frequency emissions after beam injection were concentrated in two bands below the lower hybrid frequency.

Grandal, B.↗
NASA NTRS1981

Measuring molecular flows with high-resolution stimulated Raman spectroscopy

It is proposed to use high-resolution stimulated Raman spectroscopy to directly measure high-speed molecular flow velocities in wind tunnels and in combustive chambers. A feasibility study indicates that flow speeds from Mach 0.04 up may be measured with the proposed method using available laser systems. It is pointed out that the success of the proposed technique will make it possible to measure all interesting flow parameters, i.e., species concentration, temperature, and velocity, in a time of less than 1 microsecond at a repetition rate of 10,000/s using a single experimental arrangement.

She, C. Y.↗
NASA NTRS1982

Intracellular mechanism of the action of inhibin on the secretion of follicular stimulating hormone and of luteinizing hormone induced by LH-RH in vitro

The FSH secretion-inhibiting action of inhibin in vitro under basal conditions and also in the presence of LH-RH is suppressed by the addition of MIX, a phosphodiesterase inhibitor. In the presence of LH-RH, inhibin reduces significantly the intracellular level of cAMP in isolated pituitary cells. In contrast, the simultaneous addition of MIX and inhibin raises the cAMP level, and this stimulation is comparable to the increase observed when MIX is added alone. These observations suggest that one mode of action of inhibin could be mediated by a reduction in cAMP within the pituitary gonadotropic cell.

Lecomte-Yerna, M. J.↗
NASA NTRS1981

Stimulation of body weight increase and epiphyseal cartilage growth by insulin like growth factor

The ability of insulin-like growth factor (IGF) to induce growth in hypophysectomized immature rats was tested by continuous infusion of the partially purified factor at daily doses of 6, 21, and 46 mU for an 8-day period. A dose-dependent growth of the proximal epiphyseal cartilage of the tibia and an associated stimulation of the primary spongiosa were produced by these amounts of IGF. The two highest doses of IGF also resulted in dose-dependent increases of body weight. Gel permeation of the sera at neutrality showed that the large-molecular-weight IGF binding protein was not induced by the infusion of IGF, whereas it ws generated in the sera of hypophysectomized rats that were infused with daily doses of 86 mU of human growth hormone.

Ellis, S.↗
NASA NTRS1981

Observation and measurement of molecular flow using stimulated Raman gain spectroscopy

The observation and measurement of frequency shifts in stimulated Raman gain spectroscopy resulting from subsonic molecular nitrogen flows emerging from a simple nozzle are reported. The flow velocity in the region of the measurement was determined to be 145 m/s with an accuracy of plus or minus 30 m/s. It is expected that significantly better flow-velocity resolution will be obtained in future experiments using inverse Raman scattering.

Herring, G. C.↗
NASA NTRS1982

Stimulated plasma instability and nonlinear phenomena in the ionosphere

Several hundred topside ionograms were used to study simulated wave-particle interactions in the ionosphere. The study combined the benefits of high-frequency-resolution Alouette 2 analog sounder data with advanced digital graphics techniques. The study shows that the sounder phase can cause significant plasma heating when the plasma parameter is confined to specific ranges. The observations support the Harris instability generation process and the nonlinear Landau damping maintaining process for long-duration diffuse resonances. The observations also suggest that the so-called Q resonances have characteristics which imply that generation processes in a sounder-stimulated plasma turbulence may be involved.

Benson, R. F.↗
NASA NTRS1982

Stimulation of plasma waves by electron guns on the ISEE-1 satellite

The results of the ISEE-1 satellite experiment relating to observations of the waves stimulated during electron injections, when the spacecraft is passing through the magnetosphere, the magnetosheath, and the solar wind, are discussed. It is shown that the injection of an electron beam current of the order of 10 to 60 microamperes with energies ranging from 0 to 40 eV produces enhancements in the electric wave spectrum. An attempt has been made to identify the low-frequency electrostatic wave observed below the ion plasma frequency as an ion acoustic mode, although the excitation mechanism is not clear. A coupling mechanism between the electron plasma mode and streaming electrons with energies higher than the thermal speed of the cold electron population has been proposed to explain the observations above the electron plasma frequency.

Lebreton, J.-P.↗
NASA NTRS1982

Transient effects in beam-plasma interactions in a space simulation chamber stimulated by a fast pulse electron gun

Interest in the interaction of electron beams with plasma generated by ionization caused by the primary electron beam was stimulated by the need to develop special vacuum tubes to operate in the kMHz frequency region. The experiments of Getty and Smullin (1963) indicated that the interaction of an energetic electron beam with its self-produced plasma resulted in the emission of wave energy over a wide range of frequencies associated with cyclotron and longitudinal plasma instabilities. This enhanced the thermal plasma density in the vicinity of the beam, and the term Beam-Plasma Discharge (BPD) was employed to described this phenomenon. The present investigation is concerned with some of the transient phenomena associated with wave emission during the beam switch-on and switch-off periods. Results are presented on the changes in electron energy spectra on a time scale of tens of milliseconds following beam switch-on. The results are discussed in terms of the beam plasma discharge phenomenon.

Raitt, W. J.↗
NASA NTRS1984

Atomic-oxygen stimulated outgassing (A0034)

The objective of this experiment is to determine if the impingement of atomic oxygen in near-Earth orbit is a major factor in producing optically damaging outgassed products. The expected results will be to obtain samples which have been exposed to atomic oxygen for long durations. Analysis of these samples will determine if the impingement of atomic oxygen on the thermal control surfaces stimulates a significant amount of outgassed products. This experiment will give a clearer picture of the contamination problem and will assist in assuring that future Shuttle payloads, such as the Space Telescope and High-Energy Astronomy Observatory, will not experience Skylab contamination levels. Selected thermal control surfaces will be exposed to the atomic oxygen in near-Earth orbit. Passive collecting samples will collect any induced outgassing resulting from oxygen impingement. The optical condition of the passive samples will be measured using a ground-based integrating sphere reflectometer and a directional reflectometer.

Scott, R. L., Jr.↗
NASA NTRS1984

The combined influence of stretch, mobility and electrical stimulation in the prevention of muscle fiber atrophy caused hypokinesia and hypodynamia

The morphological and biochemical changes which occur in the hind limb muscles of the rat in response to hypokinesia and hypodynamia were investigated. Hind limb cast fixation and suspension techniques were employed to study the musclar atrophy after five days of hypokinesia and hypodynamia induced by suspension, appreciable muscular atrophy was apparent, particularly in the anti-gravity muscles. The effect of passive stretching and electrical stimulation on muscle atrophy was studied. Changes in muscle protein mass were assessed with spectrophotometric and radioactive techniques. Passive stretch is shown to counteract muscle disuse atrophy. The change in the numbers of specific muscle fibers in atrophied muscles is discussed.

Goldspink, G.↗
NASA NTRS1983

Flow velocity measurements with stimulated Rayleigh-Brillouin-gain spectroscopy

Using stimulated Rayleigh-Brillouin-gain spectroscopy, velocity measurements in an atmospheric-pressure subsonic nitrogen flow with 10 percent uncertainty have been conducted. It is shown that the accuracy of the velocity measurements increases with gas pressure, making this spectroscopic technique ideal for measuring velocity and other parameters of high-pressure (greater than 1-atm) atomic or molecular flows.

Herring, G. C.↗
NASA NTRS1984

Electron-stimulated desorption study of hydrogen-exposed aluminum films

H2 adsorption of evaporated clean and H2-exposed aluminum films is investigated by using the electron-stimulated desorption (ESD) method. A strong H(+)ESD signal is observed on a freshly evaporated aluminum surface which is clean according to previously proposed cleanlines criteria. An increased H(+) yield on H2 exposure is also observed. However, the increasing rate of H(+) emission could be directly correlated with small increases in H2O partial pressure during H2 exposure. It is proposed that the oxidation of aluminum by water vapor and subsequent adsorption of H2 or water is the primary process of the enhanced high H(+) yield during H2 exposure.

Park, CH.↗
NASA NTRS1984

Enkephalin inhibition of angiotensin-stimulated release of oxytocin and vasopressin

The effect of intracerebroventricular (ICV) pretreatment with 100 ng/5 microliter leucine(5)-enkephalin (LE) on the increase in plasma oxytocin (OT) and vasopressin (VP) caused by ICV injection of 10, 50, or 100 ng/5 microliter of angiotensin II (AII) is investigated experimentally in conscious adult male Sprague-Dawley rats; the effects of water-deprivation dehydration and lactation/suckling (in female rats) are also studied. An OT radioimmunoassay (RIA) with a sensitivity of 800 fg/ml (described in detail) and the VP RIA technique of Keil and Severs (1977) are employed. Administration of AII or dehydration for 48 or 72 h cause a significant increase in OT and VP without affecting the ratio, while lactation and suckling increase OT only. LE pretreatment inhibits significantly but does not suppress the AII-stimulated OT-VP response.

Keil, L. C.↗
NASA NTRS1985

Localization of calcium stimulated adenosine triphosphatase activity in blood vessels of the skeleton

Alkaline phosphatase is an enzyme found in bone forming cells which decreases in certain bones as a result of hypogravity or non-weight bearing. This enzyme can also hydrolyze adenosine triphosphate. Therefore, an effort was made to localize calcium-stimulated ATPase by cytochemistry to determine whether altered bone cell activity might be related to changing calcium levels which occur during hypogravity. The results indicate that Ca(++)-ATPase is largely found along the endothelium and basal lamina of blood vessels, and not found in bone forming cells. This suggests that calcium regulation in the vicinity of bone formation may be modulated by the vasculature of the area.

Doty, S. B.↗
NASA NTRS1985

Reassessment of the theory of stimulated Raman scattering

A modification of the standard theory of stimulated Raman scattering (SRS) first proposed by Sparks (1974, 1975) is analyzed and shown to incorporate a possibly important physical effect; however, its original formulation is incorrect. The analysis is based on an exact numerical integration of the coupled equations of the modified theory, the results of which are compared with both the conventional theory of SRS and with one set of experimental data. A reformulation of the modified theory is suggested that leads to a gain which is in somewhat better agreement with the data than is the conventional theory.

Fralick, G. C.↗
NASA NTRS1987

Electron stimulated desorption of atomic oxygen from silver

The electron stimulated desorption (ESD) of neutral oxygen atoms from polycrystalline silver and of oxygen ions from Ag(110) has been studied. Polycrystalline Ag charged with (16)O2 and (18)O2 and bombarded by low-energy electrons (approx 100 eV) under ultrahigh vacuum (UHV) conditions emitted O atom flux levels of 1 x 10 to the 12th power/sq cm/s at a Ag temperature of 300 C. The flux was detected with a quadrupole mass spectrometer operating in the appearance potential mode. The neutral cross section at about 100 C was determined to be 7 x 10 to the -19 sq cm. Ancillary experiments conducted in a UHV chamber equipped with a cylindrical mirror analyzer and rigged for ion energy distribution and ion angular distribution were used to study O ions desorbed from Ag(110). Two primary O(+) energies of 2.4 and 5.4 eV were detected from the Ag(110) after having been dosed with 2500 L of (16)O2. It also appears that in both experiments there was strong evidence for directionality of the emitted flux. The results of this study serve as a proof of concept for the development of a laboratory atomic oxygen beam generator that simulates the gas flux environment experienced by orbiting vehicles.

Outlaw, R. A.↗
NASA NTRS1987

The effects of stimulated star formation on the evolution of the galaxy. III - The chemical evolution of nonlinear systems

The evolution of models for star formation in galaxies with disk and halo components is discussed. Two phases for the halo (gas and stars) and three for the disk (including clouds) are used in these calculations. The star-formation history is followed using nonlinear phase-coupling models which completely determine the populations of the phases as a function of time. It is shown that for a wide range of parameters, including the effects of both spontaneous and stimulated star formation and mass exchange between the spatial components of the system, the observed chemical history of the galaxy can easily be obtained. The most sensitive parameter in the detailed metallicity and star-formation history for the system is the rate of return of gas to the diffuse phase upon stellar death.

Shore, Steven N.↗